Power converter and method for operating a power converter

Abstract

A power converter includes at least three booster modules for transferring power at least from an AC input side to a DC output side. Each booster module has a galvanically separated input and output, and can be operated as a power factor correction module. The input of a first booster module is connected to the input side, and its output is connected to the output side for providing a first output current to the output side. The input of a second booster module is connected to the input side, and its output is connected to a buffer capacitor for providing a second output current to the buffer capacitor. The input of a third booster module is connected to the buffer capacitor and its output is connected to the output side for providing a third output current to the output side.

The invention claimed is: 
     
       1. A power converter for transferring power at least from an AC input side to a DC output side, the power converter comprising at least three booster modules including a first booster module, second booster module and third booster module, each of the at least three booster modules having a respective module input and a respective module output that are galvanically separated, each of the at least three booster modules being able to be operated as a power factor correction module, for drawing a sinusoidal current at its respective module input,
 wherein, in a configuration called series configuration:
 the module input of the first booster module is connected to the AC input side, and the module output of the first booster module is connected to the DC output side for providing a first output current to the DC output side; 
 the module input of the second booster module is connected to the AC input side, and the module output of the second booster module is connected to a buffer capacitor for providing a second output current to the buffer capacitor; and 
 the module input of the third booster module is connected to the buffer capacitor and the module output of the third booster module is connected to the DC output side for providing a third output current to the DC output side. 
 
 
     
     
       2. The power converter of  claim 1 , wherein the at least three booster modules are free from a power storage element that is designed to smooth current pulses arising at twice a fundamental frequency of an AC source the power converter is designed to be connected to. 
     
     
       3. The power converter according to  claim 1 , wherein the at least three booster modules have similar or identical parameters. 
     
     
       4. The power converter according to  claim 1 , comprising a controller configured to:
 control the first booster module to draw a first sinusoidal current at its input; 
 control the second booster module to draw a second sinusoidal current at its input; 
 control the third booster module to provide the third output current to complement the first output current so that a sum of the third and first output currents is at least approximately constant. 
 
     
     
       5. The power converter of  claim 4 , wherein the controller is configured to discharge the buffer capacitor to a voltage of less than 50% at each pulse of the third output current. 
     
     
       6. The power converter according to  claim 1 , comprising connections between the booster modules that can be switched, resulting in different topologies of the power converter, the power converter thereby being reconfigurable to a configuration, called three-phase parallel configuration, in which
 the inputs of the three booster modules are separate from one another, and the outputs of the three booster modules are connected in parallel to the DC output side. 
 
     
     
       7. The power converter according to  claim 1 , comprising connections between the booster modules that can be switched, resulting in different topologies of the power converter, the power converter thereby being reconfigurable to a configuration, called single-phase parallel configuration, in which
 the inputs of the three booster modules are connected in parallel to one another, and the outputs of the three booster modules are connected in parallel to the DC output side. 
 
     
     
       8. The power converter according to  claim 6 , comprising a controller configured to switch the connections between the booster modules, based on a charging current limit, a charging current set point value, a maximum rated current of the power converter and a mains configuration under which the power converter is operating,
 to be connected in the three-phase parallel configuration in the case that the power converter is connected to a three-phase AC input side; 
 to be connected in the series configuration, in the case that the power converter is connected to a single-phase AC input side, and the charging current limit is less than two times the charging current set point value and the charging current limit is less than four thirds of the maximum rated current; and 
 to be connected in the single-phase parallel configuration otherwise. 
 
     
     
       9. A method for controlling a power converter according to  claim 1 , comprising the steps of
 controlling the first booster module to draw a first sinusoidal current at its input; 
 controlling the second booster module to draw a second sinusoidal current at its input; 
 controlling the third booster module to provide the third output current to complement the first output current so that a sum of the third and first output currents is at least approximately constant. 
 
     
     
       10. The method for controlling a power converter according to  claim 9 , comprising the steps of switching connections between the booster modules, based on a charging current limit, a charging current set point value, a maximum rated current of the power converter and a mains configuration under which the power converter is operating,
 to be connected in the three-phase parallel configuration in the case that the power converter is connected to a three-phase AC input side; 
 to be connected in the series configuration, in the case that the power converter is connected to a single-phase AC input side, and the charging current limit is less than two times the charging current set point value and the charging current limit is less than four thirds of the maximum rated current; and 
 to be connected in the single-phase parallel configuration otherwise. 
 
     
     
       11. The power converter according to  claim 7 , comprising a controller configured to switch the connections between the booster modules, based on a charging current limit, a charging current set point value, a maximum rated current of the power converter and a mains configuration under which the power converter is operating,
 to be connected in the three-phase parallel configuration in the case that the power converter is connected to a three-phase AC input side; 
 to be connected in the series configuration, in the case that the power converter is connected to a single-phase AC input side, and the charging current limit is less than two times the charging current set point value and the charging current limit is less than four thirds of the maximum rated current; and 
 to be connected in the single-phase parallel configuration otherwise.